Investigation into the effect of Y, Yb doping in Ba2In2O5: determination of the solid solution range and co-doping with phosphate

In this paper we examine the effect of Y, Yb doping in Ba2In2O5, examining the solid solution range and effect on the conductivity and CO2 stability. The results showed that up to 35% Y, Yb can be introduced, and this doping leads to an introduction of disorder on the oxygen sublattice, and a corresponding increase in conductivity. Further increases in Y, Yb content could be achieved through co-doping with phosphate. While this co-doping strategy led to a reduction in the conductivity, it did have a beneficial effect on the CO2 stability, and further improvements in the CO2 stability could be achieved through La and P co-doping

Ground state of two electrons on concentric spheres

We extend our analysis of two electrons on a sphere [Phys. Rev. A {\bf 79}, 062517 (2009); Phys. Rev. Lett. {\bf 103}, 123008 (2009)] to electrons on concentric spheres with different radii. The strengths and weaknesses of several electronic structure models are analyzed, ranging from the mean-field approximation (restricted and unrestricted Hartree-Fock solutions) to configuration interaction expansion, leading to near-exact wave functions and energies. The M{\o}ller-Plesset energy corrections (up to third-order) and the asymptotic expansion for the large-spheres regime are also considered. We also study the position intracules derived from approximate and exact wave functions. We find evidence for the existence of a long-range Coulomb hole in the large-spheres regime, and infer that unrestricted Hartree-Fock theory over-localizes the electrons.Comment: 10 pages, 10 figure

Carbonate : an alternative dopant to stabilize new perovskite phases ; synthesis and structure of Ba3Yb2O5CO3 and related isostructural phases Ba3Ln2O5CO3 (Ln = Y, Dy, Ho, Er, Tm and Lu)

In this paper we report the synthesis of the new layered perovskite oxide carbonate, Ba3Yb2O5CO3. This phase is formed when 3BaCO(3):1Yb(2)O(3) mixtures are heated in air at temperatures 1000 degrees C, while above this temperature the carbonate is lost and the simple oxide phase Ba3Yb4O9 is observed. The structure of Ba3Yb2O5CO3 was determined from neutron diffraction studies and consists of a tripled perovskite with double Yb-O layers separated by carbonate layers, the first example of a material with such a structure. Further studies showed that analogous Ba(3)Ln(2)O(5)CO(3) phases could be formed for other rare earths (Ln = Y, Dy, Ho, Er, Tm and Lu). The results highlight the ability of the perovskite structure to accommodate carbonate groups, and emphasise the need to consider their potential presence particularly for perovskite systems prepared in lower temperature synthesis routes

Structure and magnetic properties of the cubic oxide fluoride BaFeO2F

Fluorination of the parent oxide, BaFeO3- δ, with polyvinylidine fluoride gives rise to a cubic compound with a = 4.0603(4) Å at 298K. 57Fe Mössbauer spectra confirmed that all the iron is present as Fe3+. Neutron diffraction data showed complete occupancy of the anion sites indicating a composition BaFeO2F, with a large displacement of the iron off-site. The magnetic ordering temperature was determined as TN = 645±5K. Neutron diffraction data at 4.2K established G-type antiferromagnetism with a magnetic moment per Fe3+ ion of 3.95μB. However, magnetisation measurements indicated the presence of a weak ferromagnetic moment which is assigned to the canting of the antiferromagnetic structure. 57Fe Mössbauer spectra in the temperature range 10 to 300K were fitted with a model of fluoride ion distribution that retains charge neutrality of the perovskite unit cel

A computational study of doped olivine structured Cd2GeO4: local defect trapping of interstitial oxide ions

Computational modelling techniques have been employed to investigate defects and ionic conductivity in Cd2GeO4. We show due to highly unfavourable intrinsic defect formation energies the ionic conducting ability of pristine Cd2GeO4 is extremely limited. The modelling results suggest trivalent doping on the Cd site as a viable means of promoting the formation of the oxygen interstitial defects. However, the defect cluster calculations for the first time explicitly suggest a strong association of the oxide defects to the dopant cations and tetrahedral units. Defect clustering is a complicated phenomenon and therefore not trivial to assess. In this study the trapping energies are explicitly quantified. The trends are further confirmed by molecular dynamic simulations. Despite this, the calculated diffusion coefficients do suggest an enhanced oxide ion mobility in the doped system compared to the pristine Cd2GeO4

Fullerenes as adhesive layers for mechanical peeling of metallic, molecular and polymer thin films

We show that thin films of C60 with a thickness ranging from 10 to 100 nm can promote adhesion between a Au thin film deposited on mica and a solution-deposited layer of the elastomer polymethyldisolaxane (PDMS). This molecular adhesion facilitates the removal of the gold film from the mica support by peeling and provides a new approach to template stripping which avoids the use of conventional adhesive layers. The fullerene adhesion layers may also be used to remove organic monolayers and thin films as well as two-dimensional polymers which are pre-formed on the gold surface and have monolayer thickness. Following the removal from the mica support the monolayers may be isolated and transferred to a dielectric surface by etching of the gold thin film, mechanical transfer and removal of the fullerene layer by annealing/dissolution. The use of this molecular adhesive layer provides a new route to transfer polymeric films from metal substrates to other surfaces as we demonstrate for an assembly of covalently-coupled porphyrins

Structure and lithium-ion dynamics in fluoride-doped cubic Li7La3Zr2O12 (LLZO) garnet for Li solid-state battery applications

The lithium-stuffed garnet Li7La3Zr2O12 (LLZO), when suitably doped, is a promising candidate material for use as a solid-state electrolyte within advanced Li-ion batteries. It possesses the thermal and mechanical stability of many inorganic ceramics, while exhibiting high Li+ ionic conductivities often associated with conventional liquid electrolytes, making it an ideal component for large-scale energy storage. However, only the high-temperature cubic phase has any meaningful Li-ion conductivity. Typically the formation of this phase is achieved through cation doping (e.g., Al3+ on the Li site) to lower the Li content and so disrupt Li ordering. However, Li-site doping, in particular, may potentially lead to some disruption of the Li-ion conduction pathways and suboptimal ionic conductivities. Consequently, other novel doping strategies involving the anion site are gaining traction, for example, F– for O2– as an alternative strategy to lower the Li content without directly blocking the lithium-diffusion pathways. For the first time, classical potential-based simulations have been employed to simulate the incorporation of fluoride anions into LLZO. Low incorporation energies have been calculated, suggesting fluoride anions are stable on the oxygen sites with a compensating lithium-ion vacancy defect. Molecular dynamics calculations suggest a definitive phase transition to the more desirable cubic phase of LLZO when doped with fluoride at temperature significantly lower than that for the tetragonal–cubic phase transition found for pure LLZO. Remarkably, the lithium-ion transport properties are shown to improve in the fluoride-doped samples particularly at low temperatures due to the stabilization of the cubic phase, suggesting anion doping of garnet systems may be a compelling alternative route to optimize the ionic conductivity

A review of metrology in lithium-ion electrode coating processes

Lithium-ion battery electrode design and manufacture is a multi-faceted process where the link between underlying physical processes and manufacturing outputs is not yet fully understood. This is in part due to the many parameters and variables involved and the lack of complete data sets under different processing conditions. The slurry coating step has significant implications for electrode design and advanced metrology offers opportunities to improve understanding and control at this stage. Here, metrology options for slurry coating are reviewed as well as opportunities for in-line integration, discussing the benefits of combining advanced metrology to provide comprehensive characterisation, improve understanding and feed into predictive design models. There is a comprehensive range of metrology which needs little improvement to provide the relevant quantifiable measures during coating, with one exception of particle sizing, where more precise, in-line measurement would be beneficial. However, there is a lack of studies that bring together the latest advancements in electrode coating metrology which is crucial to understanding the interdependency of myriad processing and product parameters. This review highlights the need for a comprehensive metrological picture whose value would be much greater than the sum of its parts for the next generation of multiphysics and data-driven models

Crystallographic and Magnetic Structure of the Perovskite-Type Compound BaFeO2.5: unrivaled complexity in oxygen vacancy ordering

We report here on the characterization of the vacancy-ordered perovskite-type structure of BaFeO2.5 by means of combined Rietveld analysis of powder X-ray and neutron diffraction data. The compound crystallizes in the monoclinic space group P2(1)/c [a = 6.9753(1) Å, b = 11.7281(2) Å, c = 23.4507(4) Å, β = 98.813(1)°, and Z = 28] containing seven crystallographically different iron atoms. The coordination scheme is determined to be Ba7(FeO4/2)1(FeO3/2O1/1)3(FeO5/2)2(FeO6/2)1 = Ba7Fe([6])1Fe([5])2Fe([4])4O17.5 and is in agreement with the (57)Fe Mössbauer spectra and density functional theory based calculations. To our knowledge, the structure of BaFeO2.5 is the most complicated perovskite-type superstructure reported so far (largest primitive cell, number of ABX2.5 units per unit cell, and number of different crystallographic sites). The magnetic structure was determined from the powder neutron diffraction data and can be understood in terms of "G-type" antiferromagnetic ordering between connected iron-containing polyhedra, in agreement with field-sweep and zero-field-cooled/field-cooled measurements